The petroleum which has been heretofore in extensive use as an energy source is now suffering a notable rise of price and threatening exhaustion of deposit. In the circumstance, the development of some other energy source capable of stable supply has constituted itself a task to be imposed on the industry. Studies are now under way for the development of techniques for effective use of such carbonaceous solids as coal, oil coke, and petroleum pitch. As actual means for effective use of such carbonaceous solids, thermal decomposition, gasification, combustion, substitution for heavy oil blown into blast furnaces in the steel-making industry, and substitution for heavy oil used in kilns in the cement industry, for example, are conceivable. In these techniques for effective use of carbonaceous solids, since the carbonaceous solids are in a solid state at normal room temperature, they are handled only with difficulty. These carbonaceous solids are not easily used effectively as desired because they have the disadvantage that the fine particles crumbling from these solids are drifted in wind to pollute the environment and threaten dust explosion. The desirability of converting these carbonaceous solids into liquids thereby ensuring ease of handling and precluding environmental pollution and dust explosion is finding growing recognition. Further for the purpose of lowering the cost of transportation, it is desirable to convert these carbonaceous solids into liquids.
For the purpose mentioned above, the conversion of a carbonaceous solid into a slurry proves to be a desirable way of ensuring effective use of the carbonaceous solid. For this slurry to be utilized for thermal decomposition, gasification, combustion, substitution for heavy oil to be blown into blast furnaces, and substitution for heavy oil to be used in kilns for cement production, it must be prepared in a highly concentrated form and, at the same time, must be prevented from inducing the phenomenon of solid-liquid separation due to sedimentation of solid particles suspended in the slurry.
In recent years, as means for converting a carbonaceous solid into a slurry, the method which effects this conversion by causing the carbonaceous solid to be dispersed in a medium such as water, methanol, or a fuel oil, for example has been proposed. To cite a typical example, the COM (coal-oil mixture) which can be transported through a pipeline is verging on practical use. Since the COM uses a fuel oil, it still has room for some anxiety about stability of supply and price. To avoid the difficulty, a highly concentrated aqueous slurry of a carbonaceous solid using water as an inexpensive and readily available medium is attracting keen attention as a highly promising approach to the effective use of carbonaceous solids.
An attempt at increasing the concentration of a carbonaceous solid in the aqueous carbonaceous solid slurry by the known method, however, results in a notable addition to the viscosity and loss of the flowability of the slurry. Conversely, a decrease of the concentration of the carbonaceous solid in the slurry results in a decline as in the efficiency of transportation and the efficiency of combustion. Further when the aqueous carbonaceous solid slurry of a lowered solid concentration is put to use in applications which require removal of excess water, the treatments for the removal of water from the slurry and the desiccation of the remaining cake call for an unduly large expense and entail the problem of environmental pollution.
Heretofore, for the solution of the various problems mentioned above, various dispersants for aqueous carbonaceous solid slurries have been proposed. Typical examples of such dispersants include such surfactants and water-soluble polymers as sodium oleate (U.S. Pat. No. 2,128,913), polyoxyethylene alkylphenyl ether (U.S. Pat. No. 4,094,810), stearylamine hydrochloride (U.S. Pat. No. 2,899,392), polyethylene oxide (U.S. Pat. No. 4,242,098), cellulose (U.S. Pat. No. 4,242,098), polysodium acrylate (U.S. Pat. No. 4,217,109), sodium lignosulfonate (U.S. Pat. No. 4,104,035), formalin condensate of alkylphenol alkylene oxide adduct (Japanese Patent Laid-Open SHO No. 59(1984)-36,537), and formalin condensate of sodium naphthalenesulfonate (Japanese Patent Laid-Open SHO No. 56(1981)-21,636). These dispersants, however, are invariably deficient in practicability because the aqueous carbonaceous solid slurries produced by incorporation thereof have no sufficient flowability and because such slurries necessitate incorporation of dispersants in undully large amounts and prove uneconomical.
An object of this invention, therefore, is to provide a novel dispersant for an aqueous carbonaceous solid slurry and an aqueous carbonaceous solid slurry composition produced by incorporation of the dispersant.
Another object of this invention is to provide a dispersant for easy preparation of an aqueous carbonaceous solid slurry possessing flowability even in a highly concentrated state.